CN102539515A - High-sensitivity detection method of normal temperature normal pressure surface assisted laser desorption mass spectrometry - Google Patents

Abstract

The invention discloses a high-sensitivity detection method for surface-assisted laser desorption mass spectrometry at normal temperature and pressure, and belongs to the technical field of mass spectrometry. The invention adopts graphite as the energy conduction material in the ionization process, and utilizes the laser desorption plasma ionization mass spectrometry device to detect various small molecule compounds. Compared with the prior art, the invention has high detection sensitivity.

Description

A high-sensitivity detection method for surface-assisted laser desorption mass spectrometry at room temperature and pressure

technical field

The invention belongs to the technical field of mass spectrometry, and in particular relates to a high-sensitivity detection method of surface-assisted laser desorption mass spectrometry at normal temperature and pressure.

Background technique

Ambient Mass Spectrometry (AMS) has gradually developed into a relatively mature mass spectrometry technology because it does not require sample preparation, can be performed under atmospheric pressure, and has no selectivity for the sample surface to be analyzed. Electrospray desorption ionization (Desorption Electrospray Ionization, DESI), real-time direct analysis (Direct Analysis in Real Time, DART), electrospray laser desorption ionization (Electrospray Laser Desorption/Ionization, ELDI), low temperature plasma probe (Low -Temperature Plasma Probe, LTP), paper spray ionization (Paper SprayIonization), etc., provide a more convenient way for the detection of small molecules and biomolecules. Taking Infrared Laser Ablation Metastable-Induced Chemical Ionization (IRLAMICI) as an example, this method combines infrared laser and DART to improve the spatial resolution of mass spectrometry. However, scientific work has been pursuing mass spectrometry methods with higher sensitivity and easier operation. However, in the mass spectrometry method of IR-LAMICI, in the process of laser desorption of surface molecules, because the energy of the laser cannot be absorbed by the molecules very effectively, the desorption efficiency is low, resulting in poor mass spectrometry sensitivity.

Contents of the invention

The purpose of the present invention is to provide a high-sensitivity detection method for surface-assisted laser desorption mass spectrometry at normal temperature and pressure. compounds with high detection sensitivity.

The detection method of laser desorption mass spectrometry provided by the present invention specifically comprises:

1. First, coat a layer of graphite on any surface of the filter paper, and use a capillary to spot the liquid sample on the surface of the graphite layer;

2. Fix the filter paper coated with the sample on the three-dimensional mobile platform;

3. Using a laser desorption mass spectrometry detection device to detect and analyze the analytes on the surface of the filter paper.

The core component (Fig. 1) of the laser desorption mass spectrometry detection device of the present invention is made up of real-time direct analysis ion source, three-wavelength pulsed laser and mass spectrometry mass detector, wherein, three-wavelength pulsed laser is used to adsorb on the graphite surface The sample molecules desorbed into gas phase sample molecules; real-time direct analysis of the ion source is used to generate metastable helium atoms, and the helium atoms interact with water molecules in the air to generate water molecule ions, and then the water molecule ions and gas phase sample molecules Proton exchange occurs and then enters a mass spectrometric mass detector for detection.

The outlet of the real-time direct analysis ion source and the interface of the mass spectrometer mass detector can be on the same straight line, the three-dimensional mobile platform is located 3-5mm below the straight line, and the filter paper with graphite-coated surface is fixed on the three-dimensional mobile platform.

The positive progress effect of the present invention is: a. Through comparison, it is found that graphite has significantly improved the detection sensitivity of analytes; b. It has universality for small organic molecules with different structures; c. This effect exists under different laser wavelengths; d. .The operation is very simple, there is no complicated sample processing process, and the whole process only takes a few minutes.

The beneficial effects and practicability of the present invention are demonstrated through the analysis of different compounds by the device below.

As shown in Figure 2, the filter paper was divided into two sections in the experiment, half of which was not coated with graphite, called "white section"; the other half was coated with graphite, called "black section". Taking myristic acid as an example, under the negative ion mode, when the laser scans the white segment, the myristic acid ion cannot be detected; The resulting ions) signal increased rapidly. The experiment was repeated three times and it was shown that the coated graphite is critical for the detection of myristic acid: no ion generation occurs in the segments without graphite. In the positive ion mode, the same conclusion was obtained for the analysis of 4-aminoantipyridine. Therefore, according to the different properties of the compounds, a total of 51 compounds were selected to verify the universality of the device for the detection of compounds with different structures in positive ion mode or negative ion mode. The results show that the presence of graphite greatly enhances the detection of both linear compounds such as myristic acid, cyclic compounds such as methyltestosterone, aromatic compounds such as 4-aminoantipyridine, and large conjugated compounds such as rhodamine B. sensitivity. Taking sebacic acid and octadecylamine as examples, the signal-to-noise ratio is less than 1 in the section not coated with graphite; while in the section coated with graphite, the signal-to-noise ratio of sebacic acid reaches 352, and octadecylamine reaches 593. Although the detection limit of each compound has not been systematically studied in this device, for anthrone, the detection limit can reach 25pg.

Description of drawings

Fig. 1 schematic diagram of experimental device;

Figure 2 is the change of mass spectrometry response before and after graphite coating on the surface, left side: a) extracted ion chromatogram (EIC) of tetradecanoic acid molecule, b) mass spectrogram before graphite coating, c) mass spectrogram after graphite coating; right side : d) the extracted ion chromatogram of 4-aminoantipyridine, e) the mass spectrogram before coating graphite, f) the mass spectrogram after coating graphite;

Detailed ways

The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples.

1. Sample preparation.

1. Cut the filter paper into a rectangle with a length × width of 100 mm × 5 mm, fix the filter paper on a glass sheet, and lightly coat a graphite layer on the surface of the filter paper with a pencil;

2. A glass spotting capillary (100mm x 0.5mm in length x inner diameter) absorbs the liquid sample solution, and spots the sample on the surface of the filter paper coated with a pencil, about one microliter per spot.

2. Sample detection and analysis process.

1. Fix the prepared sample on the three-dimensional mobile platform;

2. Turn on the three-wavelength pulsed laser (see Table 1 for the parameters). The angle between the laser emitted by the laser and the desorption surface is 45°C. After the laser energy is stabilized, the infrared laser, visible laser, and ultraviolet laser respectively have an energy of about 5mJ. , 2mJ, and 1mJ conditions, the sample molecules adsorbed on the graphite surface are desorbed into gas phase molecules; the moving speed of the three-position mobile platform is 1.5mm/s.

3. At the same time, turn on the real-time direct analysis ion source (see Table 2 for parameters), and generate metastable helium atoms at a helium flow rate of 1.0m ³ /h at room temperature or 400°C, and the helium atoms will interact with the The interaction of water molecules produces water molecular ions, and then proton exchange occurs between the water molecular ions and the gas phase sample molecules. Since the outlet of the real-time direct analysis ion source is on the same line as the interface of the mass spectrometer mass detector, the generated sample molecular ions finally enter the Agilent ion trap mass spectrometer The detector detects.

Table 1 Laser parameters

Table 2 Real-time direct analysis ion source parameters

Discharge true voltage 6000V grid electrode voltage 350V Heating temperature Normal temperature or 400℃ working gas Helium gas flow rate 1.0m ³ /h

Finally, it should be noted that the purpose of publishing the implementation is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Claims (5)

1. a laser desorption attaches mass spectral detection method, specifically comprises:

1) applies one deck graphite linings at the filter paper arbitrary surfaces, utilize kapillary that the fluid sample point is surperficial in graphite linings;

2) the above-mentioned filter paper that coats sample is fixed on three-dimensional mobile platform;

3) utilizing laser desorption to attach mass spectrometric apparatus detects the surperficial analyte of filter paper.

2. the method for claim 1 is characterized in that, in the said step 1), applies one deck graphite linings on the filter paper surface gently with pencil.

3. the method for claim 1; It is characterized in that; In the said step 3), said laser desorption attaches mass spectrometric apparatus and comprises: directly analyze ion gun, three-wavelength pulsed laser and mass spectrum mass detector in real time, wherein; The three-wavelength pulsed laser, being used for the sample molecule desorption that is adsorbed on graphite surface is the gas phase sample molecule; Directly analyze ion gun in real time; Be used to produce metastable helium atom; Helium atom and airborne hydrone effect produce the hydrone ion, between hydrone ion and the gas phase sample molecule proton exchange take place then, get into the mass spectrum mass detector subsequently and detect.

4. the method for claim 1 is characterized in that, directly analyzes ion gun outlet and mass spectrum mass detector interface in real time at same straight line, and three-dimensional mobile platform is positioned at this straight line below 3～5mm.

5. the method for claim 1 is characterized in that, said mass spectrum mass detector is an Agilent ion trap mass spectrometry detecting device.

Images